Question $1$

Which of the following constraints is not linear in a linear programming problem?

C

$2x1-\frac{1}{x2}=36$

B

$\frac{2x1+3x2-7x3}{0\mathrm{.}8x1+6x2+4x3}18$

D

$0\mathrm{.}2x1+0\mathrm{.}3x2+0\mathrm{.}4x30\mathrm{.}5x4$

A

$3x1+2x2-4x3120$